make StackingClient dispatch to either ash or desktop

ash/wm/stacking_controller.h

Index: ash/wm/stacking_controller.h
diff --git a/ash/wm/stacking_controller.h b/ash/wm/stacking_controller.h
index ae90555d2ba275164c5778cb47965e4e0ba65bb2..21611ed6faa609ca650618be76a60a571a843feb 100644
--- a/ash/wm/stacking_controller.h
+++ b/ash/wm/stacking_controller.h
@@ -5,6 +5,7 @@
 #ifndef ASH_WM_STACKING_CONTROLLER_H_
 #define ASH_WM_STACKING_CONTROLLER_H_
 
+#include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ -15,17 +16,19 @@ class RootWindow;
 }
 
 namespace ash {
-namespace internal {
 
+namespace internal {
 class AlwaysOnTopController;
+}
 
-class StackingController : public aura::client::StackingClient {
+class ASH_EXPORT StackingController : public aura::client::StackingClient {
  public:
   StackingController();
   virtual ~StackingController();
 
   // Overridden from aura::client::StackingClient:
-  virtual aura::Window* GetDefaultParent(aura::Window* window,
+  virtual aura::Window* GetDefaultParent(aura::Window* context,
+                                         aura::Window* window,
                                          const gfx::Rect& bounds) OVERRIDE;
 
  private:
@@ -44,7 +47,6 @@ class StackingController : public aura::client::StackingClient {
   DISALLOW_COPY_AND_ASSIGN(StackingController);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_STACKING_CONTROLLER_H_